1. Field of the Invention
This invention relates to an automatic focusing system of video camera, and more particularly an automatic focusing system wherein the contrast of a Y signal, which is one of image input signals of a video camera, is detected and the value of this contrast is controlled into a maximum value, thereby automatically adjusting the focus of video camera.
2. Description of the Prior Art
Prior art systems could adjust the focus of a video camera automatically. However, these prior art focusing systems have drawbacks because they use a separate optical system, such as an infrared rays emitter, an infrared ray detector and a beam splitter and or the like, and are complicated in their structure, large, in size and heavy in weight, thereby being expensive and not able to automatically adjust the focus of the camera when an object is not distinguished from its peripheral background, such as when the object is a dark surface or is positioned outside of windows or beyond wire nettings.